食品中脱氢醋酸的GC分析及降解

采用气相色谱法对乳制品干酪、小浆果草莓中食品防腐剂脱氢醋酸进行测定，并确定了试样处理方法与测定条件；考察了干酪样品中脱醋酸在贮藏期间的含量变化情况；初步得出不同条件下脱氢醋酸降解变化的一般规律。     

Understorey condition scoring of Ghanaian lowland tropical moist forest during stock survey: a technique for regulating the allowable cut in ecologically and structurally degraded production forest

Understorey condition scoring is a rapid assessment field technique for appraising and delimiting the various stages of ecological and structural decline in fire-degraded, lowland, tropical moist forest. The scoring system is designed to be incorporated into stock survey. It is simple and consistent, with only minimal time and labour requirements. The degree of degradation is assessed from the vegetation structure contained within the first 2 m of the stand's vertical profile and is assigned to one of six categories. Sample plots of 20 m radius are used to distinguish localised, degraded areas from natural forest chablis and a high sampling intensity is employed to enable accurate mapping of the forest condition. Establishing the spatial extent and degree of degradation facilitates a more appropriate determination of the allowable cut at the sub-compartmental level, thereby affording protection to affected areas of forest against further ecological and structural deterioration. In addition, the system can be used for long-term condition monitoring and targeting dry-season fire-control operations.     

微生物接种剂和酶制剂对玉米秸组成成分和瘤胃有效降解率的影响

通过玉米秸发酵试验及半体内法 ,评价了复合产乳酸菌 (植物乳杆菌 保加利亚乳杆菌 粪尿链球菌 嗜酸乳杆菌 )、酶制剂 (纤维素酶 淀粉酶 糖化酶 )、液体发酵剂 (益生菌 )单独或联合应用对玉米秸组成成分及瘤胃有效降解率的影响。结果表明 ,从整个发酵期来看 ,高剂量固体发酵剂组 (每吨秸杆添加复合产乳酸菌 2 0 g 纤维素酶 10 0 g 淀粉酶 30 0 g 糖化酶 30 0 g)、高剂量液体发酵剂组 (每吨秸杆添加益生菌 5 0 0 m L )、中性洗涤纤维 (NDF)含量略低于对照组 (P <0 .0 5 ) ;高剂量的固体发酵剂和液体发酵剂明显提高了玉米秸快速降解的干物质 (DM) (P <0 .0 5 )、NDF成分 (P <0 .0 1) ,显著降低了慢降解的 DM、NDF成分 (P <0 .0 1) ;从有效降解率来看 ,高剂量液体发酵剂组的DM有效降解率明显高于对照组及纤维素酶组 (P <0 .0 5 ) ,NDF有效降解率则比其他各组均有明显提高 (P <0 .0 5 )。     

高原湿地纳帕海水生植被调查与分析

水生植被是湿地植被的基础和重要组成部分,体现着湿地生态系统的演化和发展方向。利用3S技术和典型取样的方法,通过对纳帕海水生植被的调查表明:水生植物有32种,隶属20科,可分为挺水植物、沉水植物、浮叶植物3个植被亚型和11个群系;水葱(Scirpus palustris)、水蓼(Polygonum hydropiper)、狭叶香蒲(Tupha angustifolia)、菜(Nymphoides peltatum)、狐尾藻(Myripophyllum spicatum)等是水生植被的优势种,而具有特别重要意义的物种,如杉叶藻(Hippuris vulgaris)、小黑三棱(Sparganium simplex)的数量减少或消失;水生植被分布区范围相对较小,其组成结构出现了退化趋势。     

作用于LCC的三种微生物的筛选

采用透明圈法筛选出具有半纤维素降解能力的霉菌2株及细菌1株,并用于处理粗木质素样品。分析结果表明,3株菌对木质素均无降解能力。这对于具有LCC结构的粗木素的提纯具有研究价值。     

青藏高原江河源区生态环境安全问题分析与探讨

从江河源区气候、地理及生态系统功能的特殊性入手,对江河源区一系列自然资源、生态环境问题进行分析和评述.指出江河源区生态环境问题非常复杂,生态环境建设应该从保护生态系统入手,维持已经建立的江河源自然保护区模式,国家持续性投资于生态补偿、恢复以及相应的科学研究是江河源区生态环境长久改善的基础.重视文化教育,科技培训及推广,能给江河源区生态环境建设带来持久性的效果.在退化草地生态系统上建立家庭牧场模式的草地农业体系,改变退化草地生态功能,使之成为高效的饲草供应基地,是实现极度退化草地生态恢复和经济作用的最佳措施.江河源区生态环境威胁日趋严重,因此问题的解决需要我国政府、人民以及科技力量的共同努力.     

旱泉沟流域天然灌丛退化成因及保育对策

以祁连山自然保护区旱泉沟流域生境为研究对象,分析出气候变迁、鼠类破坏、认识偏差、超载滥牧、樵采挖药、农垦残食、利益相争等是天然灌丛退化的主要成因,以"人-草-畜"和谐发展为目标,提出了完善机制、分区治理,自然修复、持续经营,封山禁牧、育灌育草,以草定畜、划区轮牧,人工种草、合理利用,调整结构、增加收益的保育对策.     

Infectivity of scrapie prion protein (PrPSc) following in vitro digestion with bovine gastrointestinal microbiota

The influence of a complex microflora residing in the gastrointestinal tract of cattle on the prion protein plays a crucial role with respect to early pathogenesis and the potential infectivity of faeces resulting in contamination of the environment. It is unknown whether infectious prion proteins, considered to be very stable, are inactivated by microbial processes in the gastrointestinal tract of animals during digestion. In our previous study it was shown that the scrapie-associated prion protein was degraded by ruminal and colonic microbiota of cattle, as indicated by a loss of anti-prion antibody 3F4 immunoreactivity in Western blot. Subsequently, in this study hamster bioassays with the pre-treated samples were performed. Although the PrP(Sc) signal was reduced up to immunochemically undetectable levels within 40 h of pre-treatment, significant residual prion infectivity was retained after degradation of infected hamster brain through the gastrointestinal microflora of cattle. The data presented here show that the loss of anti-prion antibody 3F4 immunoreactivity is obviously not correlated with a biological inactivation of PrP(Sc). These results highlight the deficiency of using Western blot in transmissible spongiform encephalopathies inactivation assessment studies and, additionally, point to the possibility of environmental contamination with faeces containing PrP(Sc) following an oral ingestion of prions.     

Considering degradation kinetics of pesticides in plant uptake models: proof of concept for potato

BACKGROUND

Degradation kinetics of pesticides in plants are crucial for modeling mechanism-based pesticide residual concentrations. However, due to complex open-field conditions that involve multiple pesticide plant uptake and elimination processes, it is difficult to directly measure degradation kinetics of pesticides in plants. To address this limitation, we proposed a modeling approach for estimating degradation rate constants of pesticides in plants, using potato as a model crop. An operational tool was developed to backward-estimate degradation rate constants, and three pesticides were selected to perform example simulations.

RESULTS

The simulation results of thiamethoxam indicated that the growth dynamics of the potato had a significant impact on the degradation kinetic estimates when the pesticide was applied during the early growth stage, as the size of the potato determined the uptake and elimination kinetics via diffusion. Using mepiquat, we demonstrated that geographical variations in weather conditions and soil properties led to significant differences in the dissipation kinetics in both potato plants and soil, which propagated the variability of the degradation rate constant. Simulation results of chlorpyrifos differed between two reported field studies, which is due to the effect of the vertical distribution of the residue concentration in the soil, which is not considered in the majority of recent studies.

CONCLUSIONS

Our proposed approach is adaptable to plant growth dynamics, preharvest intervals, and multiple pesticide application events. In future research, it is expected that the proposed method will enable region-specific inputs to improve the estimation of the degradation kinetics of pesticides in plants. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.